Preparation of conjugated diene polymers using atecompound catalysts

ABSTRACT

Conjugated diene polymers having a microstructure consisting of about 70% of trans-1,4-structure, about 20 percent of cis-1,4structure and about 10 percent of 1,2- or 3,4-structure is prepared by polymerizing (1) at least one conjugated diene or (2) a mixture of a conjugated diene and a vinyl-substituted aromatic hydrocarbon by using an &#39;&#39;&#39;&#39;Ate-compound&#39;&#39;&#39;&#39; catalyst having the following general formula M1M2R1R2R3R4 wherein M1 is calcium, strontium or barium, M2 is zinc or cadmium, and R1, R2, R3 and R4 are aliphatic, cycloaliphatic or aromatic hydrocarbon radicals containing from one-ten carbon atoms.

United States Patent Onishi et a1. May 23, 1972 I 1 PREPARATION OF CONJUGATED 3,202,64 4/1965 Yancey ..260/93.7 ATE- ,202,64 8 1965 Yancey ..260/93.7 3,277,070 10/1960 Weynbergh etal.... .....260/94.9

COMPOUND CATALYSTS 3,365,432 1/1968 Mackenzie et a1 ..260/82.5

Inventors: Akira Onishi; Ryota Fujio; Minoru Kojima, all of Tokyo, Japan Assignee: Bridgestone Tire Company Limited,

Tokyo, Japan Filed: Sept. 8, 1969 Appl. 116.; 856,170

Foreign Application Priority Data Sept. 16, 1968 Japan ..43/66l27 260/821, 260/943, 260/880 B Int. Cl. ..C08f 1/74 Field of Search ..260/80.7, 82.1, 84.1, 94.3

References Cited UNITED STATES PATENTS 12/1964 Enk et a1 ..260/82.5

Primary ExaminerJoseph L. Schofer Assistant Examiner-Stanford M. Levin AttorneyStevens, Davis, Miller & Mosher [57] ABSTRACT haying the following general formula wherein M is calcium, strontium or barium, M is zinc or cadmium, and R R R and R are aliphatic, cycloaliphatic or aromatic hydrocarbon radicals containing from 1-10 carbon atoms.

8 Claims, No Drawings PREPARATION OF CONJUGATED DIENE POLYNIERS USING ATE-COMPOUND CATALYSTS The present invention relates to a process for preparing conjugated diene polymers which comprises contacting a monomeric material selected from the group consisting of l) at least one conjugated diene and (2) a mixture of a conjugated diene and a vinyl-substituted aromatic hydrocarbon with a catalyst (hereinafter abridged as an Ate-compound catalyst) having the following general formula MM R R R R wherein M is a member selected from the group consisting of calcium, strontium and barium, M is a member selected from the group consisting of zinc and cadmium, and R R R and R are hydrocarbon radicals selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals containing from one to ten carbon atoms.

The term conjugated diene polymers used herein means homopolymers of a conjugated diene, copolymers of two or more different conjugated dienes and copolymers of a conjugated diene and a vinyl-substituted aromatic hydrocarbon.

It has been well-known that a conjugated diene, a vinyl-substituted aromatic hydrocarbon or a mixture of a conjugated diene and a vinyl-substituted aromatic hydrocarbon can be anionically polymerized by using alkali metals of the Group I in the Periodic Table, such as, lithium, sodium, potassium, etc., or organic compounds of alkali metal as an initiator to form a high polymer. Particularly, a conjugated diene and a vinyl-substituted aromatic hydrocarbon are copolymerized in the presence of an organolithium compound in a hydrocarbon solvent to form a block copolymer consisting of a poly( conjugated diene) block and a poly(vinyl-substituted aromatic hydrocarbon)block. However, when polar compounds, such as, ether, thioether, tertiary amine, are used as one component of the solvent in the above copolymerization, random copolymers are formed, and this process is carried out commercially. In the conjugated diene polymers obtained in the above-mentioned process, it is almost impossible that the microstructure of conjugated diene unit contains trans-1,4- structure of more than 60 percent. Moreover, when organosodium compounds and organopotassium compounds are used as a catalyst, the content of 1,2- or 3,4-structure in the conjugated diene unit reaches about 50 percent.

On the contrary, there has never been hitherto known with respect to homopolymerizations of a conjugated diene, copolymerizations of two or more different conjugated dienes and copolymerizations of a conjugated diene and a vinyl-substituted aromatic hydrocarbon, in which an Ate-compound of calcium, strontium or barium according to the present invention is used as a catalyst. The reason presumably lies in that organic compounds of metals of the Group II in the Periodic Table have been considered to be non-effective for the copolymerization. It has not been reported that organic compounds of beryllium, magnesium, zinc or cadmium alone, or mixtures of these compounds can be used as a catalyst for the production of the conjugated diene polymers. Therefore, it is an unexpected new fact that the Ate-compound of the present invention can be used as an effective catalyst for the production of the conjugated diene polymers.

The characteristics of the conjugated diene polymers obtained by using a catalyst system of the present invention will be explained hereinafter.

i. Microstructure of homopolymers of a conjugated diene and copolymers of two or more different conjugated dienes:

When the Ate-compound" of the present invention is used in the polymerization, the microstructure of conjugated diene unit in the resulting polymer has about 70 percent of trans- 1,4-structure, about 20 percent of cis-l ,4-structure and about 10 percent of 1,2- or 3,4-structure. Such microstructure is considerably different from that of polymers obtained by using organic compounds of alkali metals, such as, lithium, sodium, potassium, etc.

ii. Copolymerizability of a conjugated diene and a vinyl-substituted aromatic hydrocarbon and microstructure of copolymers of said diene and hydrocarbon:

The microstructure of conjugated diene unit is substantially constant independently of the kind of metals constituting the catalyst system as in the above case (i), but the distribution of both monomer units fairly varies depending upon the kind of 5 the metals.

a. Ate-compound" of calcium:

At the first stage of the polymerization, conjugated diene mainly polymerizes, and as the concentration of the conjugated diene in the reaction system decreases, vinyl-substituted aromatic hydrocarbon mainly polymerizes. That is, the copolymerizability of conjugated diene is considerably higher than that of vinylsubstituted aromatic hydrocarbon.

b. Atecompound of strontium:

The copolymerizability of conjugated diene is higher than that of vinyl-substituted aromatic hydrocarbon as in the above case (a), that is, Ate-compound of calcium is used. However, the difference of copolymerizabilities between the two monomeric materials is smaller than the case that Ate-compound of calcium is used.

c. Ate-compound of barium:

The copolymerizability of conjugated diene is slightly higher than that of vinyl-substituted aromatic hydrocarbon. However, when Ate-compound" of barium is used, the ratio of vinyl-substituted aromatic hydrocarbon added to the copolymer chain is close to the ratio of vinyl-substituted aromatic hydrocarbon contained in the feed line. Therefore, substantially uniform random copolymers can be obtained.

iii. As seen from the above cases i and ii, when Ate-compound of barium is used, uniform random copolymers of a conjugated diene and a vinyl-substituted aromatic hydrocarbon containing about percent of 1,2- or 3,4-structure can be obtained. This is one of the remarkable characteristics of the present invention. For example, it has been known that if the content of 1,2-structure in the butadiene unit in butadiene-styrene copolymer (SBR) decreases, the glass transition temperature Tg of SBR lowers and the physical properties of SBR at low temperature improves. Moreover, the random distribution of styrene units in the copolymer chain can im prove the physical property of the butadiene-styrene copolymer as an elastomer together with the improvement of physical property at low temperature due to the above-mentioned low glass transition temperature Tg.

The Ate-compound" to be used as the catalyst of the present invention has the following general formula M M RRR R, wherein M is a member selected from the group consisting of calcium, strontium and barium, M is a member selected from the group consisting of zinc and cadmium, and R, R R and R are hydrocarbon radicals selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals containing from one to ten carbon atoms.

An explanation will be made in order to clarify the meaning of the above-mentioned Ate-compound".

When alkylmetals having the general formulas 1 M and wherein M, M, R, R R and R have the same meanings as described above, are mixed, they are reacted to form a complex. For example,

to form Ba (ZnRR R R] Thus, zinc is a bivalent metal, but the other two alkyl radicals are coordinated to the zinc to form a zincate anion Zn[RR"R R] which forms. ion pair together with B3992 in amount of the solvent used is usually within a range of 100 2,000 parts by weight, preferably, 300 1,000 pans by weight based on 100 parts by weight of the monomeric materia1.

Therefore, BaZn(R),, wherein R has the same meaning as 5 The catalyst is used in a concentration of 0.1 to 100 R R R and R is not fo d di tl f om B (R) d mmoles, preferably, 0.5 to 50 mmoles per mole of the Zn( 11),, but metallic barium is dissolved into RZnR to form monomeric m t rial- BaZn(R),,; However, this complex formation reaction The polymerization reaction can be carried out at a temproceeds formally in sucha manner that two alkyl radicals are perature within a range of about -30 160 C., but it is additionally coordinated to a normal alkylzinc, for example, preferable to effect the polymerization within a range of O- (C I-1 )Zn(C H to form a zincate ion, that is, Ate-complex 120 C. The polymerization reaction can be effected under a [Zn(C b89),,] which fonns ion pair together with Ha pressure generated autogeneously, but it is preferable to effect Such Ate-compound is defined by G. Wittig (G. Wittig, the polymerization under a sufficient pressure to maintain the Angew. Chem. 70(3), 65-71 (1958)). A well-known Atemonomeric material in a liquid state. Of course, the compound is LiAll-l wherein one hydrogen atom is coor- 15 polymerization reaction may be effected under high pressure. dinated to All-l to form [All-1 1 which forms ion pair An amount of a conjugated diene to be used for production together with Li of the conjugated diene copolymers in the present invention Among the thus defined Ate-compounds" having the can be varied within a broad range, such as, 100 10 parts by general formula M'M RR R R, ones to be used preferably in weight of the conjugated diene based on 100 parts by weight the present invention include CaZn(Cl-l CaZn(C l-i f the total monomeric materials, In another words, an CaZn(n-C H,) CaZn(n-C,,H,,) SrZn(CH SrZn(C H amount of a vinyl-substituted aromatic hydrocarbon used can SrZn(n-C l-l-,) SrZn(n-C H BaZn(C- H BaZn(n-C H-,) be varied within a range of 0 90 parts by weight. However, in BaZn(n-C,,H BaZn(n-C H,,) CaZn(C l-l SrZn(C,,l-l order to produce copolymers of a conjugated diene and a BaZn(C H,),, CaZn(cyc1ohexyl),, SrZn(cycl0hexy]) vinyl-substituted aromatic hydrocarbon having an excellent BaZn(cyclohexyl) CaCd(C H SrCd(C H,,),,, BaCdtjnproperty to be used for elastomer, it is preferable that the a als 2 s)z( 4 9)2, rZn(C H BaZn(C l-l amount of vinyl-substituted aromatic hydrocarbon in the (n-C 1-1 etc. copolymer is less than 50 percent.

The monomeric material to be used in the present invention Th rubbe y copolym r ined in a proper composition is selected from the group consisting of l) at least one conju- 3() of both monomeric materials can be compounded with natural gated diene and (2) a mixture of a conjugated diene and a rubber and the like in a conventional means. This rubbery vinyl-substituted aromatic hydrocarbon. copolymer can be molded into a final product by means of a The preferable conjugated diene contains four to 12 carbon compression molding or an extrusion molding, and can be atoms per molecule and includes, for example, 1,3-butadiene, u f r h Pr duc ion of r tire, gasket, Container, sheet isoprene, 1,3-pentadiene, 2,3-dimethyl-l,3-butadiene, 2- and methyl-1,3-pentadiene, 2-phenyl- 1,3-butadiene and l-phenyl- The invention will be explained in more detail by the follow- 1,3 butadiene. Among them, 1,3-butadiene and isoprene are irlg Ex mp sln all Examples, total monomers are 100 preferable. mmoles and part and percent mean by weight.

The vinyl-substituted aromatic hydrocarbon is a compound having eight to 20 carbon atoms per molecule, wherein at least one vinyl group is attached to carbon atoms of aromatic nucleus, and includes styrene, l-vinylnaphthalene, 3-vinyl- EXAMPLES 1 3 toluene, divinyl-benzene and the like. Among them, styrene is preferable. As the other vinyl-substituted aromatic hydrocar- A beverage bottle of 100 ml capacity was dried completely bons, mention may be made of 3,5-diethylstyrene, 4-n-propyland air in the bottle was substituted with purified nitrogen styrene, 2,4,6-trimethylstyrene, 4-phenylstyrene, 4-p-tolylthree times. The bottle was charged with 400 parts of dried styrene, 3,5-diphenylstyrene, 3-ethy1-l-vinylnaphthalene, 8- cyclohexane and 25 parts of styrene by means of an injector, phenyl-l-vinylnaphtalene, etc. and cooled to 7 8 C. The bottle was further charged with 75 The polymerization of the present invention may be efparts of 1,3-butadiene and a predetermined amount of the fected by a bulk polymerization process or by a solution catalyst shown in the following Table l, and then sealed. The polymerization process, but it is necessary that the bottle was placed in a thermostat at 50 C. provided with a polymerization system should be completely free from oxygen rotating frame and rotated for a predetermined period of time and water in both cases. to effect polymerization. The polymerization mixture was As the solvent, use may be made of aliphatic, allCyCllC and added to a large amount of 2 percent solution of phenyl-B- aromatic hydrocarbons, and these hydrocarbons containing naphthylarnine in ethanol to stop the polymerization reaction, less than 10 percent by weight of an ether compound having and the precipitated copolymer was separated and dried at 50 chain or cyclic structure. it is desirable that the hydrocarbon is C. under vacuum. liquid under usual condition of polymerization reaction, and Control experiments were carried out in the same manner hydrocarbons having not more than 20 carbon atoms, such as, as described above, except that Mg(C H,,) and Zn(C H n-pentane, n-hexane, n-heptane, n-octane, isooctane, were used respectively, which were Comparative Examples 1 cyclohexane, benzene, toluene, xylenes, tetralin, decalin, etc. and 2. are preferably used. As the ether compounds, ethyl ether, The obtained result is shown in the following Table 1. 1n propyl ether, tetrahydrofuran, 1,4-dioxane, etc., are these copolymerization reactions, the total amount of bupreferably used. tadiene and styrene was mmoles.

TABLE 1 Catalyst Polymer- Mierostrueture of butadiene unit ization Intrinsic Styrene ----A4-Y Amount time Yield viscosity content Trans-1,4 1,2 (Bis-1,4 Example number Kind (minol) (min.) (percent) [17] (percent) (percent) (percent) (percent) 1 r Blzmcnh), 1 00 40 0.24 20. 1 70.0 13.0 2. S1Z1t(CglI5) 1 50 511 0. 31 10.9. 70.4 20.1 3 r. ctlZl](C21l5)i l 50 45 (l. 28 5.1 77. 2 12.) Comp, ative mple 1 MgtC lim 2 1,200 O Comparative example 2 ZuLCQHm Z 1, 200 U In the above Table l, the intrinsic viscosity was determined When styrene contents of copolymers produced in various at 30 C. in toluene. The intrinsic viscosity described in the feed ratios of styrene are determined by the use of the abovefollowing Examples was measured under the same condition. I described infrared analysis, the obtained styrene content The microstructure of 1,3-butadiene unit and styrene conagreed very well with the theoretical styrene content in the tent in the copolymer were analyzed in the following 5 case that the conversion is assumed to be 100 percent. procedure by the use of infrared spectrophotometer. The microstructure of polybutadiene also was analyzed The intensity of infrared spectrum is shown by the following quantitatively in the exactly same procedure. formula 1 according to Lambert-Beers law. Table 1 shows that even when metals of the Group [I in the I=I,,e" 1) Periodic Table are used, Ate-compounds" of barium, stronti- ,wherein um and calcium can polymerize a mixture of 1,3-butadiene I intensity of infrared ray after passed through a sample and styrene, but Mg-alkyl and Zn-alkyl cannot initiate the 1 intensity of infrared ray before passing through the sampolymerization reaction.

le Furthermore, it can be seen from the comparison of styrene k extinction coefiicient of the sample contents of copolymers obtained in about 50 percent converc concentration of the sample sion that when BaZn(C,,l-l,,) produces a copolymer, the

z cell thickness. styrene content of which is close to the feed line (25 percent),

With respect to the absorption bands at 967 cm in trans- CaZn(C H produces a copolymer, in which 1,3-butadiene is 1,4 bond of butadiene unit, at 910 cm in 1.2 bond and at 700 mainly polymerized at the first stage of the copolymerization cm in styrene, each extinction coefficient was calculated rea ti n, and SrZn(C l-l produces a copolymer having an from a model substance by means of a 4020 grating n a intermediate property. The microstructure of butadiene unit is Speclrophommetel' made y pp Bunko The formula not highly influenced by the kind of metals, and its trans-1,4

1 is modified to obtain the following formula 2 content i hi h D=log I /1=kct (2) Therefore, the concentrations of trans-1,4 bond, 1,2 bond Examples 4- 6 and styrene can be easily calculated from the cell thickness t, the measured value of the absorbance D and the abovedescribed extinction coefiicient. The concentration of cis-1,4 bond is determined by subtracting the concentrations of trans- I I. f 5;: gzgg bond and styrene from the concen m 0 78 C. The bottle was further charged with 75 parts of 1,3-

The microstructure of 1,3-butadiene unit and styrene conbutadlene and mmole of the catalyst as shown m the tent described in the present invention are defined as follows: lowing Table and E Sealed The bottle was placfm i a thermostat kept at 70 C. and rotated to effect polymerization.

The obtained result is shown in the following Table 2.

A beverage bottle of 100 ml capacity was dried completely and air in the bottle was substituted with purified nitrogen three times. The bottle was charged with 400 parts of toluene and 25 parts of styrene by means of an injector, and cooled to TABLE 2 Microstructure of butediene unit Polymeri- Intrinsic Styrene zation time Yield viscosity content Trans-1,4 1,2 Cis-lA Example number Catalyst (min.) (percent) [1 (percent) (percent) (percent) (percent) 4." BaZn(C4Ha)-1 300 95. 0 0. 47 22. 7 70. 5 7. 8 21, 7 5. SIZH(C2 5)-l 300 97.3 0. 30 19.0 70.8 7.8 21.4 6. CflZIl(C2H5)4 300 82. 7 U. 41 10. 3 74. 8 J. 2 16. 0

cisl 4 content by wcight)= 100 Ct+ CV-l-CC Examples 7 9 Cl? In these exam les co o1 merization reactions wer f trans-1 4 content b Wei ht 100 p p y e e y g C -l-CE-lfected 1n the same manner as recipe as described in Example V 4 exce t that n-hexane was used as a solvent and the 1 2 vin 1 content b wel ht =-X 10 5O P y y g l -l polymerization time was 20 hours, to obtain a result as shown b h Cst X 100 in the following Table 3. nt Wei t styrene conte y g j y qic l TABLE 3 Microstructure of butadiene unit Intrinsic Styrene Yield viscosity content Trans-1,4 1,2 Cis-1,4 Example number Catalyst (percent) [1;] (percent) (percent) (percent) (percent) BaZn(C4Hn)-i 94. 0 0. 62 21. 3 66. 7 7. 4 25. J SrZn(CzH5)4 94. 0 0. 32 21. 1 70. 1 ll. 4 20. 5 CaZn(C2H5)4 88. l 0. 42 15. 7 73. 0 9. U 18. 0

,wherein EXAMPLE 10 Ct concentration of trans-1 ,4 bond 11'] the copolymer deter- 65 mined by infrared analysis In this Example, a copolymerization reaction was efiected Cv concentration of 1,2(vinyl) bond in the copolymer in the Same manner and recipe as described in Example determined by i f a d analysis cept that 400 parts of cyclohexane containing 5 percent of Ce concentration of cis-1,4 bond in the copolymer detertetrahydrofuran were used as a Solvent, and 1 "mole of mined by infrared analysis BaZn(C.,H,, was used as a catalyst at 50 C. for minutes, Cst concentration of styrene bond in the copolymer deterto Obtain a po y er in a yield of 61 percent. In the mined by infrared analysis copolymer, styrene content was 15.6 percent, the microstruc- The measurement of infrared spectrum was effected by disture of butadiene unit contained 70.0 percent of trans-1,4, 9.6 solving a copolymer sample in carbon disulfide and using a percent of 1,2 and 20.4 percent of cis-l,4. It was found that cell of the solution havingathickness of 0.5 mm. when a small amount of tetrahydrofuran is contained in cyclohexane, the activity of the catalyst of the invention increases somewhat, but the copolymerizability of styrene decreases somewhat.

Furthermore, when cyclohexane containing a small amount EXAMPLES 16 18 In these examples, polymerization reactions were efiected in the same manner and recipe as described in Example 4, except that butadiene were used as a monomeric material and f i g dloxane used as a Solvent the homopolymerized 1n the presence of 1.5 mmoles of catalysts. 3: were O ne The obtained result is shown in Table 4.

EXAMPLE 11 TABLE 4 A copolymerlzation reaction was effected in the same manner and recipe as described in Example 1, except that 1 Yield Intrinsic ggfi gg gh z gg g mmole of BaZn(C l-l (C 11 catalyst was used at 50 C. for Example (perviscosity w c 120 minutes, to obtain a copolymer in a yield of 73 percent. in number (Italy can) PUMA this copolymer, the styrene content was 20.5 percent and the 1fi B zmgn m 92. 0 0, 65 69, 3 10, 5 20, 2 a 17.. SrZn( H 88.9 o. 50 73.6 8. 2 1s. 2 microstructure of butadiene unit contained 69.2 percent of 18 f 821 063 76.0 15. 3 transl ,4, 9.0 percent of 1,2 and 21.8 percent of (215- l ,4.

EXAMPLE l2 EXAMPLES 19 21 A copolymefizatio" reaction was effected in the same In these examples, polymerization reactions were effected manner and Tempe as descl'lbed in Example 1, except that l in the same manner and recipe as described in Example 4, exmmole 0f a 5)4 y was used at for 300 20 cept that isoprene were used as a monomeric material and minutes, to obtain a copolymer in a yield of 77 P In thls homopolymerized in the presence of 0.3 mmole of catalysts. copolymer, the styrene-content was 21.0 percent and the Th btain d lt is shown in Table 5. microstructure of butadiene unit contained 70.1 percent of trans- 1,4, 9.3 percent of 1,2 and 20.6 percent of cisl ,4. TABLE 5 Ex. Intrinsic EXAMPLE No. Catalyst Yield viscosity A copolymerization reaction was effected in the same 19 B 1] manner and recipe as described in Example 1, except that 1 20 fi $8 1 f BaCd(C H catal st was used at 50 c for 100 r m mo e o I 2 5 4 y 21 cazn(c,1-1, 100.0 0.33 minutes, to obtain a copolymer in a yield of 67 percent. In this copolymer, the styrene content was 20.2 percent and the EXAMPLES 22 36 microstructure of butadiene unit contained 68.8 percent of I th 1 l trans-1,4, 7.8 percent of 1,2 and 21.7 percent of cis-l,4. n examp cope ymenzfmorl reactions were E 14 fected m the same manner as described in Example 1, except EXAMPL that a mixture of 55 parts of 1,3-butadiene and parts of A copolymerization reaction was effected in the same 35 styrene was used as a monomeric material and copolymerized manner and recipe as described in Example 1, except that a at 60 C. in the presence of 0.5 mmole of a catalyst. mixture of mmoles of styrene and 50 mmoles of isoprene The obtained result is shown in Table 6.

TABLE 6 Polymer- Microstructure of butadiene unit ization Styrene time Yield content Trans-1,4 1,2 Cis-l,4 Example number Catalyst (m1n.) (percent) (percent) (percent) (percent) (percent) BaZn(C4H )4 20 5. 6 32. 4 63. J 9. 2 26 9 BaZn(C4Hn)4 30 12. 2 31. 6 64. 4 7. s 27. 7 BaZmmHm 50 20.6 32. 2 63. 3- s. 1 2s. 6 BaZn(C Ha)4 10 47. 2 33. 6 62. 7 7. s 29. 5 BBZI1(C4II9)4 1, 600 95. 4 41. 7 59. s a. u 32. 2 SrZn(C2Ha)4 15 10. 4 14. 4 70. 0 8. 0 22.0 SrZn(C1H )4 25 :14. s 18. 3 70. 1 6. u 23. 0 SrZn(C2I-I )4 35 52. 3 27. 7 74. 0 7. 7 1s. 3 srzmcznpi 90 75. 5 36. s 69. 8 7. 6 22. 6 SIZ!1(C2H5)4 1, 500 J5. 4 42. 2 5S. 2 7. G 24. 2 cazmcgflpt 30 11. 7 u. 2 74. a 11.2 14. 0 CaZn(C H5)4 56 19. 2 12. 5 69. 7 13. 5 16. s CaZn 01m). 25. s 10. 1 74. 2 11. 4 1'4. 4 C8Zn CgHB 4 27. U 10. u 74. 6 10.11 14. 4 OaZn(CzH5)-1 00 40. 6 15. s 73. 1 10. 6 15.5

was used as a monomeric material and copolymerized at 50 In can be seen from Table 6 that BaZn.(C.,l-l produces a C. for 300 minutes in the presence of 1 mmole of BaZn 4H copolymer, the styrene content of which is close to the feed catalyst, to obtain a copolymer in a yield of percent. This line (45 ercent), CaZn(C H produces a copolymer, in copolymer had an intrinsic viscosity of O. l 2. which 1,3-butadiene is mainly polymerized at first stage of the copolymerization reaction, and SrZn(C H,,), produces a copolymer having an intermediate property. EXAMPLE 15 60 A copolymerization reaction was effected in the same EXAMPLES 37 39 manner and recipe as described in Example 1, except that a In these examples, copolymerization reactions were efmixture of 50 mmoles of butadiene and 50 mmoles of isoprene fected in the same manner as described in Example 1, except was used as a monomeric material and copolymerized at 50 65 that a mixture of 70 parts of 1,3-butadiene and 30 parts of C. for 300 minutes in the presence of BaZn(C l-I catalyst, to styrene was used as a monomeric material and polymerized at obtain a copolymer in a yield of 79 percent. This copolymer 52 C. had an intrinsic viscosity of 0.32. The obtained result is shown in the following Table 7.

TABLE 7 Catalyst Polym er- Microstructure of butadiene unit ization Styrene Amount time Yield content trans-1,4 1, 2 Isis-1,4 Example Number Kind (mmol) train.) (percent) (percent) (percent) (percent) (percent) 37 BaZ11(C;Hn)4 1.0 60 26.2 20.9 64.6 8.5 26.9 as, STZI1(C2H5)-1 1.0 60 78.6 21.6 74.7 8.0 17.3 39 C11Z11(C3H5)4 0 5 28. 5 7. 2 74. 5 11. l 14. 4

EXAMPLE 40 A copolymerization reaction was effected in the same manner as described in Example l, except that a mixture of 90 parts of 1,3-butadiene and 10 parts of p-vinyltoluene was used as a monomeric material, and polymerized at 60 C. for 280 minutes in the presence of 0.7 mmole of BaZn(C l-l,,) catalyst, to obtain a copolymer in a yield of 74.5 percent. It was confirmed from infrared absorption spectrum that pvinyltoluene was copolymerized.

EXAMPLE 41 A beverage bottle of 100 ml capacity was dried completely and air in the bottle was substituted with purified nitrogen three times. The bottle was charged with 400 parts of dried cyclohexane and 25 parts of styrene by means of an injector, and cooled to 78 C. The bottle was further charged wlth75 parts of 1,3-butadiene and 0.3 mmole of BaZn(C.l-l,,) and then sealed. The bottle was placed in a thermostat at 60 C. provided with a rotating frame and rotated for 20 hours to effect polymerization. The polymerization mixture was added to a large amount of 2 percent solution of phenyl-B- naphthylamine in ethanol to stop the polymerization reaction, and the precipitated copolymer was separated and dried at 50 C under vacuum. The resulting copolymer was colorless and extremely rubber-like.

The obtained result is shown in the following Table 8.

TABLE 8 Yield (36) 91.5 Styrene content 24.0 Trans-L4 (76) 68.0 1,2 7.4 Cis-l,4 (16) 24.6 Recovery of oxidative degradation product (9%) Glass transition temperature (C) 72 by DSC method In order to determine the random property of the copolymer obtained in the present invention, the randomness of styrene chain was calculated from the recovery of polystyrene according to the following oxidative degradation method.

This oxidative degradation was effected according to a method disclosed by LM. Kolthoff, in which osmium tetroxide and tert-butyl hydroperoxide are used (Journal of Polymer Science, Vol. 1, page 429 (1946)). That is, when the copolymer of the present invention is oxidatively degraded by the use of osmium tetroxide catalyst and tert-butyl hydroperoxide, only butadiene unit is degraded and styrene unit remains undecomposed. When the degraded styrene chain has a polymerization degree of less than about 5, the

styrene chain is soluble in methanol, while when the degraded styrene chain has a polymerization degree of more than about 5, the styrene chain is insoluble in methanol. Thus, the randomness of the copolymer can be determined from the recovery of styrene chain insoluble in methanol.

The term recovery of styrene chain" herein means weight percentage of styrene chain recovered as insoluble part through oxidative degradation of the copolymer" based on the total styrene content in the copolymer before the oxidative degradation.

In the copolymer obtained in this Example 41, the recovery after oxidative degradation is 0 percent, which shows that the copolymer is a random copolymer containing no long styrene chains.

Furthermore, the glass transition temperature Tg of this copolymer is 72C, which is considerably lower than that (T -56) of commercially available SBR obtained by emulsion polymerization.

What is claimed is:

l. A process for preparing conjugated diene polymers consisting essentially of contacting a monomeric material selected from the group consisting of l) at least one conjugated diene having four-l2 carbon atoms and (2) a mixture of a conjugated diene having four-l2 carbon atoms and styrene, the amount of said styrene being 0 parts by weight based on parts by weight of the total monomeric materials, at a temperature in the range of -30 to C, in the presence of aromatic hydrocarbon solvent selected from the tgrou consisting of benzene, toluene, xylene and tetralrn m e a sence of oxygen and water with a catalyst consisting essentially of an Ate-compoundhaving the following formula:

M W R R R R wherein M is a member selected from the group consisting of calcium, strontium and barium, M is zinc, R, R, R and R are aliphatic hydrocarbon radicals containing from one to ten carbon atoms, the amount of said catalyst being in the range of 0. l to 100 millimoles per mole of said monomeric material.

2. A process according to claim 1, wherein said monomeric material is 1,3-butadiene.

3. A process according to claim 1, wherein said monomeric material is isoprene.

4. A process according to claim 1, wherein said monomeric material is a mixture of 1,3-butadiene and styrene.

5. A process according to claim 1, wherein said catalyst is bariumzinctetrabutyl.

6. A process according to claim 1, wherein said catalyst is strontiumzinctetraethyl.

7. A process according to claim 1, wherein said catalyst is calciumzinctetraethyl.

8. A process according to claim 1, wherein the amount of said catalyst is in the range of 0.5 to 50 millimoles per mole of said monomeric material. 

2. A process according to claim 1, wherein said monomeric material is 1,3-butadiene.
 3. A process according to claim 1, wherein said monomeric material is isoprene.
 4. A process according to claim 1, wherein said monomeric material is a mixture of 1,3-butadiene and styrene.
 5. A process according to claim 1, wherein said catalyst is bariumzinctetrabutyl.
 6. A process according to claim 1, wherein said catalyst is strontiumzinctetraethyl.
 7. A process according to claim 1, wherein said catalyst is calciumzinctetraethyl.
 8. A process according to claim 1, wherein the amount of said catalyst is in the range of 0.5 to 50 millimoles per mole of said monomeric material. 